It's something like this -- in my actual theme comments' code.. within the 'foreach' statement... but i'm not sure that in my code below I'm actually referring to the userid of the commenter...

Here's the officialcommenter code:
<li class="comment <?php echo (is_wpuser_comment() ? ' commentOfficialUser' : ''); ?>" id="comment-<?php comment_ID() ?>">



Here's my suggested new code -- basically scratching officialcommenter out of there:
<li class="comment

<?php
    if ( $user_id ) {
        $userdata = get_userdata($user_id);
        $user = new WP_User($user_id);
        $post_author = $wpdb->get_var("SELECT post_author FROM $wpdb->posts WHERE ID = '$comment_post_ID' LIMIT 1");
    }

    if ( $userdata && ( !$user->has_cap('level_9') && $user->has_cap('level_1') ) ) {
        // The user is an author, not admin.
        echo ' commentExpert';
     }
     elseif ( $userdata && ( $user_id == $post_author || $user->has_cap('level_9') ) ) {
        // The user is post author OR the admin.
        echo ' commentOfficialUser';
     }
     else
        // The user is a nobody.
        echo '';
?>

" id="comment-<?php comment_ID() ?>">